Coming back to this topic, we were finally able to convert VRML meshes 
into Collada files that are displayed fine in RViz and rendered smoothly.

There was indeed a problem with the meshes that Meshlab stored. Even 
though it displayed the normals and they were in the file, the meshes 
were not rendered smoothly. My confusion came from looking at the PR2 
stl-meshes, which RViz also renders "blocky", while the collada files 
are fine. Opening up one of these Collada files in Meshlab and merely 
saving it again "corrupted" the normals somehow so that the mesh could 
no longer be rendered smoothly. Autodesk 3DS converted some parts fine, 
but the resulting files also had some shading issues (probably resulting 
from messing up material color, texture, and texture coordinates).

Our VRML meshes with crease angles could be finally converted into a 
nice 3D robot model in Collada format using Blender, even preserving 
multiple colors and textures. Maybe that helps someone with the same 
kind of problems.

Best regards,
Armin

-- 
Armin Hornung                              Albert-Ludwigs-Universität
www.informatik.uni-freiburg.de/~hornunga   Dept. of Computer Science
HornungA@informatik.uni-freiburg.de        Humanoid Robots Lab
Tel.: +49 (0)761-203-8010                  Georges-Köhler-Allee 79
Fax : +49 (0)761-203-8007                  D-79110 Freiburg, Germany